Remove the stems from the shiitake mushrooms. Carefully clean the tops, then cut into thick slices. Melt the butter in a sauté pan over a high heat, without browning. Lightly sauté the shiitakes and mushrooms for approx. 5 min., then sprinkle with salt. Remove the mushrooms from the pan. Add the rice, onions and vegetable stock to the pan. Simmer over a low heat under a tight-fitting lid for approx. 12 min. Remove the pan from the heat and let the rice and onions rest without removing the lid for approx. 12 min.
Meanwhile, melt the butter in a frying pan until golden. Brown the steak for about 1 min. on each side and sprinkle with salt and pepper. Continue cooking over a low heat for about 10 min. – turning occasionally. Remove the flank steak and set aside, covered, for about 10 min.
Stir the mushrooms, chives and half the cheese into the rice and heat through. Season to taste.
Cut the flank steak into thin, diagonal slices – across the grain. Pour the risotto into a warm serving bowl, sprinkle with chives and serve with the rest of the cheese on the side.
Rice with wild mushrooms also makes a lovely vegetarian dish. Without the flank steak, the dish serves 3.